Ripe Xenopus oocytes in 1st meiotic prophase when incubated with progesterone in vitro undergo meiotic cell division. The mechanism of this trigger for cell division has been shown to be a decrease in cyclic AMP levels. Current studies are designed to investigate adenylate cyclase and phosphodiesterase activities to determine which are involved in mediating the decrease in cyclic AMP. Other studies are characterizing a surface receptor for progesterone involved in the proliferative response and which may be linked to the adenylate cyclase system. These studies will provide new and important information on the linkage between the cell surface, cyclic AMP, and the normal signals for cell proliferation.